1. Field of the Invention
This invention relates to a liquid jetting method and a liquid jetting apparatus. More particularly, this invention relates to a liquid jetting method and a liquid jetting apparatus that can yield a film having a uniform thickness and have high usage efficiency of the liquid. The invention further relates to an electro-optical apparatus substrate production method and an electro-optical apparatus production method using the liquid jetting method.
2. Description of the Related Art
Coating methods such as spin coating, die coating, roll coating, and the like, are known for forming a relatively thin film on a semiconductor substrate, a liquid crystal display device or a color filter substrate. Among these coating methods, the spin coating method is generally believed to be the most optimal for forming a thin and uniform film of a micron order.
According to the spin coating method, a to-be-coated substrate on which a film is to be formed (hereinafter referred to as “substrate”) is held on a spin chuck and a liquid to be applied, such as a resist material, is applied drop-wise to the center of the substrate. The substrate is then rotated at a high speed so that the resulting centrifugal force diffuses the liquid from the center of the substrate in an outer circumferential direction to thereby form a film.
The spin coating method is more suitable for forming a film having a small distribution of film thickness and a uniform thickness than other coating methods. However, because about 90% or more of the liquid applied drop-wise is diffused from the surface of the substrate to its surrounding and is leveled, the method is not free from the drawback that the liquid is consumed in vain and is not advantageous from the aspect of both environment and economy.
Therefore, JP-A-H08-250389 discloses a thin film formation apparatus and a thin film formation method for suppressing wasteful consumption of the liquid and forming a film having a uniform film thickness even when a substrate is warped and includes concavo-convexity, as shown in FIG. 26. More particularly, in the thin film formation apparatus and the thin film formation method, a plurality of nozzles of an ink jet system for intermittently jetting a predetermined amount of a liquid is arranged in a predetermined direction. These nozzles are moved linearly and relatively in a direction crossing at right angles with the arrangement direction to apply the liquid onto a substrate.
JP-A-H08-314148 discloses a production method of a resin film as shown in FIG. 27. More particularly, to reduce portions having a non-uniform film thickness (that is, beads) and to expand a useful area, this reference describes a production method of a resin film including the steps of arranging a resin film on a substrate by a nozzle of an ink jet system, and locally controlling a temperature of an outer edge portion by second heating means disposed separately from first heating means in a process step of heating and drying the resin film by the first heating means.
JP-A-H09-10657 discloses a thin film formation apparatus to form a thin film having a predetermined film thickness with reduced waste of a coating solution as shown in FIG. 28. More particularly, this reference discloses a thin film formation apparatus including (1) an ink jet head having a plurality of fine nozzles for jetting a coating solution against a substrate, (2) a rotation means for rotating the substrate, (3) a relative movement means for moving relatively the ink jet head between a proximity region of a rotating shaft and a spaced-apart region and (4) a relative movement control means for decreasing the relative movement speed of the relative movement means from the proximity region of the rotating shaft toward the spaced-apart region, or decreasing an angular velocity.
JP-A-2001-174819 discloses a coating film formation method and a film formation apparatus to form a film having excellent uniformity of a film thickness while reducing a material cost as shown in FIG. 29. More particularly, the reference describes a coating film formation method and a film formation apparatus including (1) a step of supplying a film material in a droplet form or a mist form by an ink jet nozzle to a film formation region of a substrate placed horizontally inside a processing chamber and (2) a step of rotating the substrate to which the film material is supplied so as to diffuse the film material on the substrate to form a coating film.
As shown in FIG. 30, JP-A-2000-288455 discloses a resist application apparatus to efficiently form first and second resist thin films formed of a plurality of resist materials having different densities. More particularly, the reference discloses a resist application apparatus provided with (1) a data storage portion for storing a position of a first region for forming a first resist thin film and a position of a second region for forming a second resist thin film, (2) a first resist coating portion for forming the first resist thin film in the first region, (3) a second resist coating portion for forming the second resist thin film in the second region, and (4) a resist coating control portion for conducting control so that a plurality of resist materials having mutually different densities can be selectively applied.
The formation apparatus and the formation method of the thin film formed of the liquid disclosed in JP-A-H08-250389 is suitable when the substrate is rectangular in shape and its size is specified because the nozzle of the ink jet system is moved linearly and relatively in the predetermined direction. However, this method may be wasteful of the liquid when the liquid is applied to a circular substrate or to substrates having different sizes.
Columnar spacers are disposed in some cases on the substrate. In this case, the columnar spacers become obstacles for sufficiently diffusing the liquid, and formation of the thin film with a uniform thickness becomes more and more difficult.
The production method of the resin film disclosed in JP-A-H08-314148 must locally control the temperature of the outer edge portion by disposing the second heating means in the heating and drying step of the resin film. Therefore, the production apparatus becomes large, the production cost becomes high and the production time becomes elongated. The method that locally controls the temperature of the outer edge portion by disposing the second heating means has low usage efficiency of the coating solution and moreover, cannot easily form a thin film having a uniform thickness inclusive of the film thickness distribution near the center of rotation of the substrate.
In the thin film formation apparatus disclosed in JP-A-H09-10657, the liquid is applied while the angular velocity or the moving speed is controlled, but fine control is difficult in practice. Since this art is basically intended to jet a predetermined amount of the coating solution from the ink jet head, the moving speed of the head or the angular velocity must be reduced at the outer peripheral portion of the substrate, and a long time is necessary for printing. When the viscosity of the coating solution and its solid content vary depending on the ambient condition, it becomes difficult to jet a predetermined amount of the coating solution from the ink jet head. It is eventually difficult to form a thin film having a uniform thickness while usage efficiency of the coating solution is improved.
The coating film formation method disclosed in JP-A-2001-174819 supplies the film material either in the droplet form or in the mist form to the entire surface of the substrate at one time. Therefore, when a predetermined amount of the coating solution can always be jetted from the ink jet head, the method is effective for forming the thin film having a uniform thickness. However, when the viscosity of the coating solution and its solid content vary depending on the ambient condition, the problem develops in that the film thickness near the center of rotation of the substrate is likely to become great.
Further, the resist coating apparatus disclosed in JP-A-2000-288455 is an effective application means for forming a plurality of resists having different densities or the like within a short time, but is not free from the problem that the film thickness is likely to become great near the center of rotation of the substrate.